Crossbar drafting and layout machine based on flexible guide elements



Jan. 16, 1962 D. G. FALCONER CROSSBAR DRAFTING AND LAY 3,016,615 OUT MACHINE BASED ON FLEXIBLE GUIDE ELEMENTS Filed Oct. 25, 1957 ,2 Sheets-Sheet 1 1 INVENTOR WEE Jan. 16, 1962 D. G. FALCONER 3,015,615

CROSSBAR DRAFTING AND LAYOUT MACHINE BASED ON FLEXIBLE GUIDE ELEMENTS 2 Sheets-Sheet 2 Filed Oct. 25, 1957 IN VENTOR United States The machine according to the invention comprises two main elements: The first is a rolling bar-like element further referred to as the crossbar, which can move across the drafting board or layout board, further referred to simply as the board, in such a manner that it will at all times be parallel to itself.

The second main element is a carriage, on which a number of horizontal or vertical scales, or a triangle or templates of any kind can be mounted. Each of these elements can have a protractor. The carriage can move back and forth along said bar-like member. Thus, a two-dimensional movement is obtained.

The aforesaid scales, triangle or template, with or without protractor, will further be referred to as the drafting aids.

According to the invention the aforesaid members are so designed and disposed that the following outstanding advantages are obtained:

(1) The machine can be moved over the board in such a way that no part of it will be in sliding contact with the board. Smudging of the paper is therefore completely eliminated.

(2) Books and pencils lying on the board will not interfere with the movements of the machine.

(3) The weight of the hand and the forearm are en tirely supported by the machine.

(4) The drafting aids can with a simple movement be completely removed from the board.

(5) The machine requires less space than a conventional drafting machine. The board can, with its back or sides, be placed right up against a wall, while the machine can still reach every part of the board.

(6) Its accuracy is greater than that of conventional machines having a large number of bearings or pivots or which depend on friction for maintaining accurate alignment.

(7) The machine is, compared to conventional drafting machines, extremely simple and rugged and can be manufactured at only a small fraction of the cost of a conventional drafting machine.

(8) The machine has an extremely light feather touch operation.

Further objects and advantages and how these are, according to the invention, obtained will become apparent from the following description, reference being had to the accompanying drawings wherein a few preferred forms of the invention are shown.

In the drawings:

FIG. 1 is a top View of the board with the drafting machine mounted on it.

FIG. 2 is a side view of the board with the drafting machine mounted on it. The crossbar is shown in section.

FIGS. 3 and 4 show two views of the end of the crossbar with the wire wrapped around it.

FIGS. 5 and 6 show two views of a modified construction of the ends of the crossbar and modified method of wrapping the guide elements around it. In FIGS. 5 and 6 tapes are used as guide elements instead of guide-wires.

FIG. 7 shows a modification of the embodiment of FIGS. 5 and 6.

Basic principle of the invention The machine basically consists of two members. One

MildfilS ice member, the so-called cross bar, denoted in FIGS. 1 and 2 by numeral 1 is a bar-like member of circular cross-section disposed across the board, substantially parallel to one of the sides of the board 11. It can be moved across the board parallel to itself by rolling it over the board. In this rolling action, it is guided by means of a pair of guide elements in a manner which will be described below. In FIG. 1 these guide elements are denoted by numeral 9.

The second member, the carriage denoted in FIGS. 1 and 2 by numeral 6, carries the drafting aid. In FIGS. 1 and 2 this drafting aid consists of two scales 7 and 8. Carriage 6 can slide back and forth along crossbar 1.

As shown in FIGS. 1 and 2 the carriage 6, disposed on crossbar 1, is aligned on the same by a wedging action caused by its own gravity, and the weight of the hand and arm of the operator moving the carriage. Normally any drafting aids attached to it touch the board 11 over their full area. When the operator is moving the carriage, and it is desired that the drafting aids do not touch the board, the carriage can be tilted so that no part of it or the drafting aid will touch the board.

Guidance of the crossbar; first modification According to the invention, the crossbar 1 is kept parallel to itself in its rolling action across theboard by means of two wires 9 strung along the edge of the board 11 and wrapped around the grooved roller or sheave units designated as a whole by reference numeral 2, which are connectedly mounted on the crossbar 1, as shown in FIGS. 1 and 2.

FIGS. 3 and 4 give a more detailed view of the rollers 2, each comprising a cylindrical section 3 by means of which the aggregate comprising the crossbar It and the rollers 2 rests on the board 11. The wire 9 rests in the groove 5 (see FIG. 4) disposed between cylindrical section 3 and outer flange part 4. In FIG. 4 the wire is wrapped around this groove only once. However, the wire can be wrapped two or even three times around the groove 5, thus increasing the friction between the wires 9 and the roller units 2, which is responsible for the maintenance of alignment parallel to itself of the crossbar.

In order to maintain accurate alignment, it is required that the wire be kept under sufiicient tension either by a spring or by weights, as shown in FIGS. 1 and 2. Here, the wires 9 are attached to the rectangular support members 12 and run along the edge of the board 11, over the cylindrical support members It to the weights 13, which maintain the desired tension.

Guidance of the crossbar; second modification FIGS. 5 and 6 show a different modification of this invention. Here two pairs of tapes are used as guide elements, one pair for each end of shaft 1. In FIGS. 5 and 6 the two tapes 19 and 20 are wrapped radially around the double sheave 16 in the grooves 17 and i3 respectively. The innermost winding of each of these tapes 19 and 28 is immovably anchored to the bottoms of their respective grooves 17 and 18, for example by means of a suitable adhesive.

Somewhat like the modification of FIGS. 1 and 2, the outer end of one tape of each pair of guide tapes is anchored to a fixed support at one side of the board 11 as in FIGS. 1 and 2, and the other tape of each pair of guide tapes runs over one of the cylindrical supports it) in FIGS. 1 and 2 to weights 13 as in FIGS. 1 and 2, which maintain the proper tension in each pair of these tapes. As the crossbar 1 rolls back and forth over the board one of each pair of tapes winds and the other one LI unwinds or vice versa depending on the direction of movement of the crossbar.

Since the diameter of the topmost winding of two adjoining tapes varies, as the crossbar moves over the board, the weights 13 may travel up and down over a not inconsiderable distance.

This variation in diameter likewise causes an anomaly in speed between the peripheral velocity of the sheaves 16 at every diameter of these windings and the-linear velocity of the crossbar over the board. The crossbar and sheaves 16 are therefore supported on the board by means of cylindrical sleeves 15 slidably mounted for rotation on cross bar 1' and positioned adjacent to each of the respective sheaves 16. The sleeves 15 roll over the board and the crossbar 1' rotates in the sleeves 15.

PEG. 7 shows a modification very similar to the modification of FIGS. 5 and 6, with the exception that wires are used instead of tapes. The two wires 21 and 22 wind and unwind axiaily in grooves 17 and 18' of sheave 16'.

While only a few modifications have been shown, the invention includes all modifications and variations encompassed by the scope of the appended claims.

What I claim is:

l. A drafting machine comprising a drawing board having opposite parallel edges, a crossbar shaft extending across and above the board surface perpendicular to said edges, a single roller disposed concentrically upon and adjacent each of the opposite ends of said shaft and positioned for rolling contact with the marginal portions of the respective opposite board edges, said rollers being sized to hold said shaft out of contact with the surface of said board, a sheave secured to each end of the shaft beyond the said edges of the board, a pair of guide wires secured at one end of each to a corner of the board at an end of the corresponding opposite edges thereof, and each wrapped about a corresponding sheave, means for tensioning each of said Wires in a position parallel to and beyond the corresponding board edge to constrain the shaft for motion parallel to itself and to hold said rollers in contact with the board margins, and a drafting instrument guide slidably mounted on said shaft for motion therealong.

2. A drafting machine in accordance with claim 1, in which said rollers are fast on the shaft.

3. A drafting machine in accordance with claim 1, in which said rollers are fast on the shaft, and in which said pulleys have substantially the same diameter as said rollers.

4. A drafting machine comprising a drawing board having opposite parallel edges, a crossbar shaft extending across and above the board surface perpendicular to said edges, a single roller concentrically disposed upon said shaft adjacent each of the opposite ends thereof and positioned for rolling contact with the marginal portions of the respective opposite board edges, saidrollers being sized to hold said shaft out of contact with the surface of said board, a sheave secured to each end of the shaft beyond the said edges of the board, flexible inextensible tension filament means secured at one end of each to a corner of the board at an end of the corresponding opposite edges thereof, and each in wrapped relation to a corresponding sheave, means for tensioning each of said filament means in a position parallel to and beyond the corresponding board edge, and a drafting instrument guide slidably mounted on said shaft for motion therealong.

References Cited in the file of this patent UNITED STATES PATENTS 2,048,221 Redding July 21, 1936 2,488,284 Froelich Nov. 15, 1949 FOREIGN PATENTS 4,341 Great Britain Feb. 20, 1913 110,776 Sweden May 30, 1944 873,219 Germany Apr. 13, 1953 

